1. Field of the Invention
The invention concerns a sliding shaft surgical instrument.
2. Description of the Related Art
A sliding shaft instrument of this type is known from U.S. Pat. No. 5,273,519 or corresponding DE 41 15 937 A1. This surgical sliding shaft instrument includes a guide element adapted for receiving a carriage. The sliding shaft instrument further includes a grip element, which is comprised of a stationary grip part, of which one end is provided with an arm pivotably connected with the guide element and releasably connectable to the guide element. Further, a moveable grip part is provided, which is pivotably linked to the arm, and which is in engagement with the carriage via a push part extending through a slit or through-hole in the arm, for operation thereof. Further, a compression spring is provided between the two grip parts, in order to pretension the moveable grip part in a rest position. Via a locking mechanism, the connection between the arm and the guide element can be released. The sliding shaft instrument further exhibits a rotation means for adjustment of the angular position of the work carriage.
In order to operate the carriage via the push part, the proximal end of the carriage is provided with a rod-shaped projection, on the end of which a ball-shaped projection is provided. In order to be able to move the carriage upon movement of the moveable grip part, this ball-shaped projection must be seated in a corresponding receptacle of the push part.
To do this it is however necessary to be able to observe a seating process from the outside. For this reason, the guide element is provided with a through-hole or window. This construction is not only expensive since various construction components must be precisely dimensioned with respect to each other, it also causes the seating process of the individual parts to be difficult and time-consuming.
U.S. 2,113,246 discloses a surgical instrument in which a compression spring is integrated in a carriage, which pretensions a moveable grip part in a starting position. For change-out of the carriage, this is seated upon a saddle, wherein a circular longitudinal section must be positioned with a thereto connecting shoulder and an oppositely lying segment positioned on a rib-shaped projection of the shoulder. Subsequently, a closing part is pivoted over the work carriage and locked with the shoulder. At the same time, the moveable grip part, the upper end of which forms a take-along fork, is introduced in a ring-notch or recess of the moveable part of the carriage, wherein the moveable part must be displaced or slid against the action of the compression spring and temporarily held in a particular position in order to make possible the seating upon the fork of the moveable grip part.
It is considered to be disadvantageous, that the seating of the work carriage is comparatively difficult and inconvenient to accomplish. There is also the danger, that during the attempt of seating the moveable part upon the fork under pretension of the spring, that this escapes upwardly and jumps out of the shoulder, before the locking part pivots back and can be locked closed. =p Further, the instrument is so conceived, that for operation of the moveable mouth part, the two grip parts must be pulled apart. These have grip-eyes at their lower ends, without which the operation of the instrument would not be possible. The movement direction is ergonomically inconvenient and makes difficult a targeted and precise force transmission. For the application of greater forces, it is in certain cases even necessary to use both hands to pull the grip parts apart at the grip eyes.